Object locating system



Jan. 16, 1951 2,537,952

R. l. ANDERSON 013111301" LOCATING SYSTEM Filed Jan. 14, 1944 2 Sheets-Sheet 1 '35 TRANSMITTER 400- REPITITION RATE AZIMUTH INDICATOR SWEEP VOLTAGE PHASE ADJUSTER GATE ccT.

GATED VIDEO SIGNALS 90 PHASE SHIFT SYNCI'IRON I-' ZING NETWt-w INDICATOR ELEVATI O N L HORIZONTAL SWEEP VOLTAGE IO0- SINUSOIDAL POWER SUPPLY 400- POWER SUPPLY FIG.I

FIG.2

VERTICAL CENTERING AAAA - HORIZONTAL CE NTERING FOCUS VIDEO SIGNAL INTENSITYJ INVENTOR ROBERT I. ANDERSON ATTORNEY Jan. 16, 1951 R. I. ANDERSON 7,

OBJECT LOCATING SYSTEM Filed Jan. 14, 1944 2 Sheets-Sheet 2- Patented Jan. 16, 1951' UNITED STATES PATENT OFFICE.

Robert I. Anderson, Alameda, Califi, assignor to The Sperry Corporation; a. corporation of Dela- Ware Application J anuary' I4, 1944; Serial No. 518327 7" 9 Claims.

which the condition of exact alignment oira;

target may be distinguished from the absence ofanytarget, or the failure of any inputv signal to be received by the apparatus.

A further object of the invention is to provide an arrangement for indicating the angle of'devia-tion by matching of received pulses.

Still another object of the invention is toprovide forseparation of azimuth and elevation indicating pulses;

Still another object of the invention is to pro-- vide an-arrangement for the indication of phenomena of a recurrent nature byan oscilloscopehaving a sub-synchronous time sweep.

other and" further objectslandi advantages: will become apparent as thedescription' proceeds;

carrying out my. inventionin its preferred form. I utilize a pulsed microwave transmitter with a receiver appropriate thereto, and means for rotating the beam. or radiation pattern over which the microwave. energy is transmitted'and received. for the purpose of makingv manitest the presence of a target or an object to be located by the reflection of' signals from such an object. I' provide apparatus responsive to the relative strengths of signals reflected from either side of the beam-rotation axis for the purpose of indicating the angular deviation of the object from the axis about which the radiation pattern or beam; isbeing' rotated. In order to' produce a single: pulse in; each quadrant of'thespace in which the microwave beam is being rotated, the repetition rate. of: the: pulse transmitter is madefour times theiangu-l'ar speed of revolution of the microwave beam. Separate azimuth and elevation indicators are provided which. maybe of the cathode-ray oscilloscope type, and. these are provided with a" sweep voltage; synchronouswith the speed of rotation of. the microwave beam and therefore; sub synchronous with respect to: the received. pulses. The received pulses are applied to;- the signal; defiectionci'rcuits: of the indicators and the. timeesweepzcircuitsi thereof aresupplied with sine-waves which arein'quadrature" so that one: indicator produces a pair of pulses which match when thecenter line of the apparatus. or

axis of rotation of; the microwave beam is directed toward. the target in. azimuth and the other indicator producespulses which are matched. when the axis of rotationis directed toward the target in elevation.

A. better understanding of the invention will be afforded by the following detailed description considered in connection. withv the accompanying drawings in which;

Fig. l is a schematic blockdiagramof one."

embodiment' of my invention;

Fig. 2 is an electric circuit diagram of one of the indicators-represented in Fig. 1;

Figs. 3A, 3B and 3C are graphs illustrating? a phase relationship. between the: received. pulses and .the oscilloscope. deflection voltages;

Fig. 4 is. a perspective diagram illustrating: themanner in which matching pulses: are obtained on the oscilloscope screen, elevation pulses are. eliminated. from the azimuth screen; and. azimuthv pulses are eliminated'from the elevation screen; and

Figs. 5A. and-5B to 8A and 8B are diagrams illustrating the appearance of the oscilloscope screen and the hypothetical positions bGYOIIdIthG screen: of: the pulses actually eliminated fromv the oscilloscope screen. under various conditions. of'angular deviation of a target.

Like reference characters are utilized throughout the drawings to designate like parts.

As in apparatus heretofore known, the apparatus. illustratedain' Fig. 1 includes a pulse microwave transmitter ll..for projecting a beam [2 of microwave. radiant energy, and a receiver l3 of the vacuum-tube. type, e; g;, for responding to. reflections: of suchv pulses in case the microwave beam. l2" should be intercepted by a target [4 causing reflection of the projected microwave energy; As in apparatusi heretofore known, I may also employ a. radiator. 15 of the. dipole and parabolic reflector type which is common to the: transmitter H and the receiver. [3' with suitable means (not shown) for preventing. direct transfer of. energy from the transmitter H to the receiver 13.

As in apparatus heretofore known, the frequency of the transmitter H may be such as tomake desirable the use" of; transmission lines It of the hollow pipe wave guide type for: connecting the transmitter H and the receiver 13- to the=radiator l5.

distinction such previously known apparatus the illustrated apparatus includes means for rotating the radiation pattern l2 of the transmitter II and receiver I3 about an axis of rotation I? together with means I8 for synchronizing the transmitter II and gating the receiver I3 so as to cause a single pulse to be transmitted and received after the radiation pattern I2 has executed each predetermined fraction, e. g., each quarter revolution about the axis I1. Any desired means may be provided for effectively causing the rotation of the radiation pattern I2 about the axis IT. For simplicity in the drawing it is assumed that this is accomplished by mounting the radiator I so that the beam center line I9 is slightly oblique with respect to the axis of rotation I1 and by providing means such as a rotatable hollow shaft 2| driven by a synchronous motor 22 through gearing 23 for physically rotating the radiator I5.

It will be understood, however, that it may be more convenient to rotate only a portion of the radiator I5, or provide other means for causing rotation of the radiation pattern I2 without actual rotation of the entire radiator I5.

Although my invention is not limited to the use of a particular radio frequency or particular repetition rate of pulses, I have found that satis-' factory results may be obtained when the microwave energy has a wavelength of 3 to centimeters by utilizing a repetition rate of 400 cycles per second, for example. When such a repetition rate is desired a 400-cycle power supply 24 may be provided with a synchronizing connection I 8 to the transmitter II, for causing the transmitter I I to produce a train of microwaves having a relatively short duration such as one-half microsecond, for example, every 2500 microseconds.

For synchronizing the pulse repetition rate with the angular speed of revolution of the radiation pattern I2, the motor 22 may be a synchronous motor and a 100-cycle power supply 25 may be provided having a synchronizing connection 25 between it and the 400-cycle power supply 24. Since the means for synchronizing the 400-cycle power supply with the 100-cycle power supply is not a part of my invention it need not be illustrated or described in detail herein. A suitable synchronizing arrangement is described in the copending application of Walter Dean, Serial No. 499,213, filed August 19, 1943, now U. S. Patent No. 2,435,958, issued February 17, 1948, and is assigned to the same assignee as the present application.

In order that angular indications of the position of the object I4 with respect to the axis Il may be produced with separate indications in azimuth and elevation, a pair of indicators 2'? and 28 is provided. These indicators contain suitable control circuits, to be described hereinafter, and cathode ray oscilloscope tubes having indicating screens 29 and 3|, respectively.

To permit selection of only the desired signal, a gate circuit 32 is preferably provided, which supplies sensitivity gates or voltage pulses to the receiver I 3 which are synchronized with the repetition rate of the transmitter I'I It will be understood that the receiver I3 may be of a known type in which control of voltage at a suitable point such as a screen grid or cathode terminal controls the sensitivity. As indicated schemati cally a synchronizing connection 33 is provided between the gate circuit .32 and the synchronizing line II! to the transmitter I I.

It will be understood, however, that the representation of synchronizing means in the drawing is only schematic and that any suitable known means or arrangement for synchronizing the gate circuit and the pulse repetition rate may be employed.

The receiver I 3 is provided with an output connection or channel 34 at which gated video signals appear, and branch connections 35 and 36 from the channel 54 are made to the vertical deflection circuits of the azimuth indicator 2'! and the elevation indicator 28.

In order that indicators 2! and 28 may be provided with a sinusoidally varying horizontal or time sweep voltage, the power supply 25 is preferably such as to produce a sinusoidal voltage. An output connection 31 from the powersupply 25 is branched to form lines 38 and 35 connected to the horizontal sweep circuits of the indicators 21 and 28, respectively. Suitable means are provided for introducing a quadrature relationship between the voltages supplied over the lines 38 and 39. For-example, a phase shifter 4| may be interposed in one of these lines; however, it will be understood that if a quarter phase power supply is utilized, separate connections from the phases may be made to the lines 38 and 39, thus obviating the need for any separate phase shifter.

Since the diagram of Fig. 1 is only schematic it is to be understood that my invention is not limited to the details of the schematically indicated means for interconnecting, phasing or synchronizing the various elements shown in the diagram.

Since the azimuth and elevation indicators 21 and 28 may be substantially identical, only one of them need be described. In the form represented in the circuit diagram of Fig. 2, each indicator comprises a cathode ray tube 42, a pair of cycle input terminals, viz., the sweep wave input terminals 38, a pair of video signal input terminals 35, a source of unidirectional voltage having positive and negative terminal 44 and 45, respectively, an adjustable phase shifter 46 for adjusting the proximity of indicated pulses, and a suitable means for adjusting and selecting various voltages to be applied to the tube 42.

The tube 42 maybe of substantially conventional form having an anode 4?, an indirectly heated cathode 48, suitable control electrodes such as a focusing electrode 49, an intensity-control grid 5I and suitable beam deflection means. As illustrated, the beam deflection means takes the form of a pair of electrostatic deflection plates 52 and 53 for producing a vertical deflection, and a second pair of electrostatic deflection plates 54 and 55 for producing horizontal deflections.

It will be understood that the tube 42 is of the type in which a cathode ray beam (not shown) is emitted by the cathode 48, and strikes a point on the screen 29, determined by the potential on the electrostatic deflection plates 52 to 55.

For providing voltages of suitable potential and for adjustability of certain of these voltages, a potentiometer 56 may be provided comprising a resistance connected between the D. C. input terminals 44 and 45 with an intermediate point 51 rounded.

For adjusting the beam intensity an adjustable tap 56 may be provided on the potentiometer 56, and may be connected to the intensity-control grid 5!, and for beam focusing an adjustable tap 59 may be provided on the potentiometer 53 and connected to the focusing electrode 49. The cathode 48 is connected to a terminal 50 near the negative end of the potentiometer 56.

alternate lEoribeam centering a pair .of centering potentiometers :56! and :62 maybe connected between the positiverterminal at or the-D. Qrpower supply source,. andea terminal fiathereof which-is onrthe negative side of the ground. terminate} The potentiometer .Bl ,isr rovlded-avith a'tap fiiiconnected :to orient the vertical plates error vertical centering, and the potentiometer 6,2;isprovided yvithan adjnstab'letapzfificonnected to .one of the horizontalfleflection plat/55154 ,forhorizontalcenter'mg. .Preferably byepass .condensers E! are connected between-the centering taps 1G5 and=fi6 and the ground connection.

-The remaining vertical deflection plate-5.3 may be grounded to the anode i-l, whereas therre maining horizontal deflection plate .55 is grounded through a resistor 68.

The sweep wave terminals 38 are coupled to the horizontaldeflection plates 54 and 55 through the adjustable phase-shifter 46. As shown, the phase shifter 46 may comprise a transformer 69, having a secondary winding "H coupled to the deflection plates .54 and 55 and having a tapped primary winding 12. The entire winding 1:2 'is connected in series witha phase-splitting con-' denser :13 and a phase-adjusting rheostat "M. A portion of the winding T2 is connectedfin series with the .rheostat 1:4 to the sweep=wave input terminals 38.

Thevideo signalinput terminals 35 are coupled to .the ungrounded vertical deflecting plate 52 through a coupling condenser 11.

As the radiation pattern 12 of the radiator iii of Fig. 1 -is rotated by the motor 22, its axis of symmetry l9 describes a cone of revolution and the beam l2 rotates between two extreme posi tions in any one plane. If the horizontal be regarded as the plane of the paper, for the sake of'illustration, the full line of representation of the beam I2 is assumed to be the. extreme righthand position; and the extreme left-hand position is represented by a pattern l2" shown'in dotted lines.

'The synchronizing connections i8 and .25 are so adjusted, with respectto the physical position of the stator of the motor 22, that pulses are produced by the transmitter H when the beam l2 is in'the upper and lower positions. Accordingly, pulses will also be produced when the beam is in the 'two positions at 90 degrees from the upper and lower positions, thatis to say, ,in the extreme right and extremeleft positions.

Referring to Fig. 3A, it will be observed that one complete scanning cycle'l8, that is, the time for the radiation pattern ['2 to .make a complete revolution about its axis of revolution l"l,. 'is four times the time interval l9 between thereceived pulses which are represented in Fig. 3A by curves Bla, b, c, d, collectively referred to hereinafter by the reference numeral 8!.

The curves 8] represent the shape .ofthe video signal output of the receiver l3 with voltage measured in .a vertical directionin .thegraphof Fig. 3A, and time duration .measured in the-horizontal direction.

The sweep wave voltages applied .,to the sweep Wave circuitsof theazimuth indicatorZJ and the elevation indicator 2% .are shown in Figs. 3B and 3C..resp.ectively. -Asshown, theazimuth voltage 33 lags approximately -90 degrees behind the elevation voltage 3.0, and thephase relationships are so adjusted, Such as by phaseshifterfi .(iEig. 2), that the maximum points andzeropointsof the deflection voltage waves .of .Figs. 3B .and 3.0

correspond -very..nearl but not exactly :to :the

instants "at-which .the received pulses occur.

Referring to Figs. 3A, 3B andEC, :it :Will :be observed that video signals, or :received pulses 8 l occur twice for each-cycle during the approx-imate times :of ,zero voltage of eithersweep wave and likewisesuchvideopulses occur twice during .the approximate .times of maximum'voltage ofa sweep "wave. :However, the video received pulses always have positive polarity whether the sweep voltage is positive or :negative.

Considering first the azimuth indication with reierence'to Figs. 3A,-3B and 5B,.if videopulses occurred exactly at the instants 32 and 8.3 .of zero sweep voltage the video pulses produced onthe screen at the center would be superimposed. However, the phase adjustment isa'ltered slightly so :thatthe two'signals that and Bib at the-center of the screen are separated, one with slightly negative sweep voltage, the other with slightly positive sweep voltage. For distinguishing the video pulses corresponding to the four different angular-positions of the microwave-beam t2, the letters a, 'b, c andzd-are added to .the'reference numeral 81.

The requisite slight dephasing of theazimuth deflection voltage pf :Fig. 313, with respect .to the radio signals of Fig. 3A, may be accomplished by suitable adjustment of the phase shifter 46 of Fig. 2.

It will be understood that for-clarity in the drawing the spacing between the pulses Blwand Sib in Fig. 5B is exaggerated. The magnitude of the :azimuth deflection voltage of .Fig. 3B is made great enough to sweep the beam -.of the tube 52 beyond the edges of the screen 29.

.Since there'are four video signals, orreceived pulses 8|, for each cycle of the sweep voltage, two of thepulses will appearon screen 29 near the center when the sweep voltage is substantially zero,:and the other two pulses will occur when the :oathoder-aybeam is swept beyond the screen 253 to the extreme left'and to the extreme right by the maximum positive and negative peak valuesof the sweep voltage indicated at 84 and 85 in Fig. 3B. The hypothetical :positions relative to screen 29 of these side pulses which do not appear on the screen are indicated by the vertical lines 810 and Bid in Fig. 5B. The relationship between thepositionson or relative to the screen 29 and the times of occurrences of the pulses Bio, 851), Bio and Bid, is represented by the perspective diagram of Fig. 4. Actually the-beam is swept back and forth along a straight line on the screen 2-9 by-the sweep voltage when the signal voltage or voltage on the vertical defiection plates 52 and 53 is zero, or constant. However, for the sake of illustration, the sweep path is represented in Fig. lby an ellipse 86. In looking in the direction of the arrow along .an azimuth line ,of .sightB-l, the azimuth indicating pulses Bio .and 8th will appear nearly superimposed, whereas two elevation indicating pulses 8 i c and 8 l dappear to theiextreme-leftanditothe extreme right.

The relative heights of the azimuth pulses-.8.l;a andfllb serve .as .an indication of the angular deviationof the target i (Fig.1) from the beam axis of rotation 17. If, as indicated in Fig. 1, the target 14 is to the right .of the axis of rotation ii, ,a stronger reflected pulse will be received when the .beamaxis leis at the extreme .right than when the beam axis isat-theextreme left. Accordingly, one of the video :signals eat :the center .of the screen, preferably the iright hand signal 8lb, appears stronger than the left-hand signal am. An indication representing this condition is illustrated in Fig. 6B.

It will be understood that the adjustment of the phase shifter 46, of Fig. 2, determines which pulse is to the right and which to the left, but preferably the adjustment is so made that the stronger pulse appears on the right when the target is on the right of the beam axis of rotation l1.

Referring to Figs. 3A, and 5A, it will be apparent that a similar action takes place with respect to the pulses 8&0 and did, indicating elevation. Thus, when the axis of rotation ii of the microwave beam lies in a horizontal plane passing through the target it, signals of equal strength will be received in the receiver is when the beam axis I9 is in its uppermost and lowermost positions, causing the pulses 85c and 8ld appearing at the center of the screen 3! of the elevation indicator to have equal height. I this case the azimuth indicating pulses @Ia and 8lb will occur when the cathode ray beam is beyond the limits of the screen 3i and will not appear on the screen although the hypothetical positions are indicated in Fig. 5A.

Figs. 63 and 6A represent the indications obtained in the screens 29 and 3| of the indicators 2! and 23 when the beam axis of rotation ii is properly centered with respect to the object It in elevation, but not in azimuth.

Figs. 7A and '73 represent the indications produced when the target H! deviates from the axis of rotation I1, both with respect to azimuth and elevation.

Referring to the perspective diagram Fig. assuming that the elevation line of sight 88 is in the direction of the arrow, it will be observed that by slight dephasing of the elevation sweep voltage of Fig. 30, the elevation pulses c and Bid are caused to appear slightly to the left and right, respectively, of the center of the elevation screen. A range gate may be used so that only targets within a predetermined band in range will be presented to the indicators.

The indicating system illustrated serves not only to indicate the deviation of the beam axis of rotation I! with respect to the direction of the target l4, but also indicates whether or not any target is present within the area swept by the revolving beam 2. For example, if no target is present so that no signals are received by receiver 13, because no microwaves are reflected, both indicators will have their screens blank as indicated in Figs. 8A and 8B. The presence of two balanced signals or pulses on the screens 29 and 3|, when the beam axis of rotation H is exactly on the target, and the absence of any indications on the screen when there is no target, enables the operator of the apparatus to detect the absence of a target immediately instead of being confused by what might appear to be a centered indication if a continuously present deflectible spot or pointer were employed to indicate angular deviation of a target from a deadahead direction.

It will be understood that apparatus such as illustrated in the drawings may be employed either for indicating the deviation of a target from a fixed line of sight, or for enabling the entire apparatus to be realigned to point toward the target in case the axis of rotation I! is made adjustable in direction by a suitably pivoted mounting arrangement for the apparatus.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now believe to represent the best embodiment thereof, but desire to have it understood that the apparatus shown and described is only illustrative and that my invention may be carried out by other arrangements.

What is claimed is:

1. An object locating system, comprising in combination means for projecting and receiving microwave beams on a rotatable radiation pattern, means for pulsing the beams at a frequency which is a multiple of the speed of rotation of the radiation pattern, and a twodimensional indicator with means for deflecting a trace in one dimension in response to received pulses and, a sine wave generator for continuously sweeping said trace in the other dimension at a frequency corresponding to the speed of rotation of the beam radiation pattern, whereby pulses corresponding to difierent angular positions of the radiation pattern may be indicated in proximity but with pulses corresponding to other positions of the radiation pattern separated from said first-mentioned pulses.

2. Apparatus as in claim 1 with a sweep of suflicient amplitude to eliminate all of the indicated pulses except the first indicated pair of pulses.

3. An object locating system, comprising in combination means for projecting and receiving a rotatable microwave beam, means for pulsing the beam with a repetition rate four times the speed of rotation of the beam, and a twodimensional indicator with means for deflecting a trace in one dimension in response to received pulses and means for deflecting the said trace in the other dimension at a sweep rate equal to the rotational speed of the beam, whereby four signal pulses are applied to said indicator for each sweep cycle, two of the pulses produced when the beam is in extreme opposite angular positions being indicated in proximity, and the other two pulses of the sweep cycle being separated from the first two.

4. An object locating system, comprising in combination means for projecting and receiving a rotating microwave beam, means for pulsing the beam at a repetition rate four times the speed of rotation of the beam, a two dimensional indicator with means for deflecting a trace in one dimension in response to received pulses, means for sweeping said trace back and forth in the other dimension at a sweep rate equalling the speed of rotation of the beam, and means for fixing the phase relationship between the trace sweep and the beam pulsing such that two alternate pulses in each sweep cycle occur at instants of nearly zero sweep, whereas the other two pulses of the sweep cycle referred to as side pulses occur at instants of maximum positive and negative sweep, whereby two of the pulses give adjacent nearly coincident indications in the center of the indicator.

5. Apparatus as in claim 4 in which the sweep magnitude is made sufiicient to eliminate the side pulse indications.

6. An object locating system for indicating azimuth and elevation deviation from a refer ence direction, comprising means for transmitting and receiving a microwave beam, means for causing rotation of said beam around an axis serving as a reference direction, means for pulsing the beam at a repetition rate four times the speed of rotation of the beam, a pair of 'osci1-' 9 loscope-type indicators for indicating azimuth and elevation deviation, respectively, each having deflection circuits for producing trace deflections in mutually transverse dimensions, means for suppling received pulses to one of the deflection circuits of each of said indicators, means for cyclically energizing the remainin deflection circuits of said indicators substantially in quadrature with a frequency equalling the speed of rotation of the beam to provide oscilloscope sweeps, and means for fixing the phase relationship between the pulses and oscilloscope sweeps so that alternate pulses occur when the sweep of one trace is very nearly but not exactly zero and when the sweep of the other trace is at positive or negative maximum value, whereby received pulses corresponding to two extreme angular positions of the rotating beam occur in the center of each indicator screen, and the other two pulses are swept to the side.

7. Apparatus as in claim 6, in which the sweep magnitude is made suflicient to sweep the side pulses beyond the oscilloscope screento eliminate them from view.

8. Apparatus as in claim 6, in which phase shifters are provided in the sweep circuits for adjusting the spacing between center signals'on the screen.

9. In combination, means for receiving pulsed radio signals, variable-directivity antenna means for varying the intensity of said received signals with a periodicity harmonically related to the periodicity of said signal pulses but such that successive signal pulses occur at diiferent directivities of said antenna means, an oscilloscope with a pair of deflection circuits for producing trace deflections in transverse-dimensions, connections for applying said received signal pulses to one of said deflection circuits, and a continuous sine wave sweep generator connected to the other of said deflection circuits and having a periodicity equal to that of said antenna means, whereby comparable indications corresponding to a plurality of said received signal pulses are produced by said oscilloscope. J

ROBERT I. ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,130,032 Robins Sept. 13, 1938 2,189,457 Archer Feb. 6, 1940 2,344,745 Somers Mar. 21, 1944 2,345,932 Gould Apr. 4, 1944 2,355,363 Christaldi Aug. 8, 1944 2,366,353 Roberts Jan. 2, 1945 2,402,168 Lifschutz June 18, 1946 2,403,429 Anderson July 9, 1946 2,422,361 Miller June 1'7, 1947 

